The present invention relates to a trailing edge flap assembly for an aircraft, and more particularly to such a flap assembly that permits change of wing camber aft of the wing structural box, and also provides a slotted Fowler flap for high lift during low speed operation.
There are any number of devices in the prior art to change the wing camber for the purpose of gust load alleviation, improved climb and cruise lift-to-drag ratio (for fuel economy) and improved maneuverability. However, a highly cambered wing trailing edge will have flow separation on the upper wing surface when operating at high angles of attack. Therefore, in general these prior attempts at variable camber trailing edge devices have had poor low speed, high lift capability.
To accomplish high lift during low speed operation, there are also devices in the prior art to deploy a slotted Fowler flap. With air passing from beneath the airfoil through the slot formed by the flap and the wing, and over the flap, the Fowler flap can be positioned at relatively high deflection angles and provide relatively high lift for low speed operation.
A search of the prior art has disclosed a number of patents showing various arrangements for variable camber wings and also for trailing edge flaps. These are as follows.
U.S. Pat. No. 1,567,531, Magni, discloses in FIGS. 1 through 8 variable camber wing, but no trailing edge flap. In FIGS. 9 through 12, there is shown a simple hinge trailing edge flap, but not combined with variable camber.
U.S. Pat. No. 1,803,915, Parmele, shows a variable thickness wing.
U.S. Pat. No. 1,846,146, Roacheville, also discloses a variable thickness wing. At the trailing edge of the wing, there is a simple hinge, non-slotted flap.
U.S. Pat. No. 2,352,062, Zap, discloses a number of trailing edge configurations. In FIGS. 1 through 6, there is a hinge mounted blown flap. In FIGS. 8 and 9, there is shown a blown aileron. In FIGS. 11 through 16, there is shown a track mounted trailing edge flap mounted on curved tracks, and in one configuration with a hinged spoiler. In FIGS. 17 through 20, there is shown a trailing edge flap having a track mounted along the lower surface of the flap. This track in turn rides on rollers mounted to a flap support member, with the flap support member being pivotally mounted. This arrangement permits the flap to be moved into three principal locations, namely: a first flap retracted position, shown in FIGS. 18 and 19; second, a flap extended position (but not deflected) as shown in FIG. 19; and third, a position where the flap is extended and deflected downwardly. However, this arrangement does not show how a flap assembly can also be used effectively to accomplish variable camber for the trailing edge of the wing.
U.S. Pat. No. 3,076,623, Lyon, shows a variable thickness wing with an unslotted trailing edge flap in a straight track.
U.S. Pat. No. 3,127,130, Lyon, also shows a variable thickness wing. This wing has a variable camber flex trailing edge. There are some flap members pivotally mounted to the lower surface of the wing, which are presumably provided for speed brakes.
U.S. Pat. No. 3,179,357, Lyon, discloses yet another variable thickness and variable camber wing. The trailing edge portion has a hinge mounted element without Fowler motion.
U.S. Pat. No. 4,053,124, Cole, shows trailing and leading edge devices, but without a Fowler flap. Variable camber is achieved by a linkage system positioned largely within the flap member.
It is an object of the present invention to provide an effective flap assembly which has the capability of changing the camber of the wing, but also has the capability of functioning as a slotted Fowler flap for high lift during low speed operation.